JPH027280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a permanent magnet type rotor comprising a rotor equipped with a permanent magnet and a stator equipped with two sets of stator windings through which two-phase currents each having a phase difference of 90 degrees flow. The present invention relates to a stepping motor, and its purpose is to improve its operating characteristics and increase its response speed with a simple configuration.

In general, a stepping motor has a structure in which the rotor and stator magnetic poles each have pole teeth, and the stator has multiple windings, and the rotor is activated by sequentially passing current through the multiple windings. Rotate by a specified angle in sequence. In such stepping motors, when the energization control device that switches the energized windings is controlled using pulse signals, the number of input pulses and the rotation angle of the motor are proportional, and the order of energization of multiple windings is changed to control forward and reverse rotation. It has excellent features as a servo motor such as easy operation.

In particular, since the number of input pulses and the rotation angle are proportional, a major feature is that the servo mechanism can be configured with a simple device using an open-loop control system that does not use position detection devices such as shaft encoders or potentiometers. Due to the above characteristics and advances in transistors, ICs, etc., stepping motors have come to be widely used in NC machines, computer peripherals, information communication equipment, etc.

However, the operation of a stepping motor is basically vibratory, with the rotor repeatedly starting and stopping for each pulse input, and in open-loop control, the pulse signal that specifies which winding to excite is unilaterally applied from the outside. Since it has nothing to do with the current position of the rotor, when driving a large load or accelerating rapidly, the rotor may not be able to follow up sufficiently and may step out. If the rotor steps out, the open loop control method The advantage that the input pulse and rotation angle are proportional is lost.

To prevent this step-out, a closed-loop control system that detects the current position of the rotor by some means and energizes the next winding at the optimal timing can be used, and even at fairly high speeds, there will be no step-out. It can be followed.

However, in the conventional closed-loop control system, it was necessary to attach a shaft encoder to the stepping motor in order to detect the position of the rotor. Particularly when an optical shaft encoder is used, there are drawbacks such as the encoder itself being expensive, requiring a large number of man-hours for installation and adjustment, and causing installation errors.

Except for the above-mentioned defects, the stepping motor of the present invention does not require a shaft encoder, and detects the position of the rotor from the speed electromotive force induced in the stator windings as the rotor rotates, and determines which windings should be energized. The feature is that it is possible to specify the wire and control the energization at the optimum time.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventional embodiments and embodiments of the present invention will be described below with reference to the drawings.

1 to 4 are explanatory diagrams showing the structure, operation, and driving device of a conventional four-phase permanent magnet stepping motor.

1 and 2, 10 is a stator yoke, 11 is a stator magnetic pole, 12 is a stator winding, and 13 is a stator yoke.
is an end bracket, 14 is a bearing provided on this end bracket 13, 15 is a rotating shaft, 16, 17
18 are the rotor yokes 16 and 17 made of magnetic material, which are spaced apart from each other in the axial direction.
A rotor consisting of permanent magnets inserted between the two.
The stator yoke 10 has a stator magnet 11-1 on its inner surface.
~11-8 are arranged to protrude radially at equal pitches, and each stator magnetic pole has stator windings 12-1 to 12-8.
The rotor yokes 16 and 17 are wound with pole teeth arranged at equal intervals on the outer periphery of the rotor yokes 16 and 17, and are arranged opposite to each other with a gap in the inner periphery formed by the tips of the stator magnetic poles.

The pole teeth of the rotor yokes 16 and 17 are shown in Figure 2 a and b.
As shown in the figure, they are placed 1/2 pitch apart from each other.

FIG. 3 is an exploded view illustrating the operation of the stepping motor shown in FIGS. 1 and 2, and FIG. 4 shows an outline of an open-loop drive device for driving the stepping motor.

The stator windings 12-1 to 12-8 shown in FIG. 3a are each set of two windings connected in series, separated by 180 degrees from each other, as shown in FIG. 3b. The first phase φ ₁ to the fourth phase φ ₄ are energized and controlled by an open-loop drive device 4 comprising a pulse generation circuit 1, a four-phase sequence circuit 2, and a four-phase drive circuit 3, as shown in FIG. The operation of the conventional stepping motor shown in FIGS. 1 and 2 will be explained with reference to FIG. 3a. FIG. 3a shows a state in which the first phase φ ₁ is energized. That is, when the first phase φ ₁ is energized in the direction AB→ from terminal A to terminal B, N poles are generated at magnetic poles 11-1 and 11-5, and pole teeth S-1 and S-6 on the rotor yoke 17 side are generated. and pole teeth N-3 and N on the rotor yoke 16 side
-8 are lined up. Next, the second phase _φ2 is energized and the first
When phase φ ₁ is de-energized, 12-2 and 12-6 are energized, magnetic poles 11-2 and 11-6 are formed, and pole teeth S-2 and S-7 of rotor yoke 17 become stator magnetic poles. 11-2 and
11-6 are lined up, respectively, and the rotor moves to the right by 1/2 of the width of the pole teeth. Furthermore, if the third phase φ ₃ is energized and the second phase ₂ is de-energized, the magnetic poles 11-3 and 11-7 are aligned with the rotor yokes S-3 and S-8, respectively, and the pole teeth are further adjusted to 1/1/2. Step 2 widths to the right. In this way, the method in which the adjacent phase of the currently excited phase is excited, the current in the currently excited phase is de-energized, and only one phase is always excited is called the one-phase excitation method, and the step angle at this time is the basic step angle. becomes. When the excitation phase switching order changes from φ ₂ to φ ₁ , the rotation direction is reversed.

Next, when the first phase φ ₁ is excited and the second phase φ ₂ is also excited at the same time, and both phases are excited, the rotor's pole teeth are the first phase φ ₁ , the second phase φ ₂ , and the attraction of both phases. It receives a force and stops at a position midway between both phases, and this position is at an angle of 1/2 step from the position where the first phase _φ1 is excited. A method in which two phases are excited together in this manner is called a two-phase excitation, and a method in which one-phase excitation and two-phase excitation are alternately repeated is called a one- and two-phase excitation method, and the excitation can be made in steps of 1/2.

Figure 5 shows the relationship between the excitation state of each phase and the rotor stopping point (stable point), where P ₁ to P ₄ are the stable points of one-phase excitation, and P' ₁ to P' ₄ are the stable points of phase excitation. Stable point, also P′ ₁ ~ P′ ₄
is the stable point during two-phase excitation. In Fig. 5, it is detected that the first phase φ ₁ is excited and the rotor is stopped at the P ₁ position, and the second phase φ ₂ is excited by this detection signal, and the rotor reaches the P ₂ position. If the system detects this and excites the third phase _φ3 , the rotor will rotate continuously and can run freely without inputting pulse signals from the outside. In this system, the detected position of the rotor is P ₁ to _{P 4} or
Since P′ ₁ to P′ ₄ , a detection device for this point is required.

In the present invention, stator windings φ ₁ and φ ₃ shown in FIG. 3b are connected in series to form stator winding L ₁ , φ ₂ and φ ₄ are connected in series to form stator winding L ₂ , and As shown in Figure 6, the stator winding of this stepping motor
Generating windings G ₁ and G ₂ are insulated and provided overlapping L ₁ and L ₂ ,
A transformer T ₁ T ₂ is provided outside the stepping motor,
The mutual electrical constants of the primary winding l ₁ and the secondary winding l ₂ of the transformers T ₁ and T ₂ are the corresponding stator windings L ₁ and L ₂ and the electric winding G ₁ of the stepping motor, respectively. , G ₂ is set to be equal to the mutual electrical constant.

In addition, the stator winding L ₁ and the primary winding L ₁ of the transformer T ₁ are connected in series and connected to the drive circuit, and the two of the transformer T ₁ are connected in series.
The next winding L ₂ and the power generation winding G ₁ are connected in series so as to have opposite polarities, and the detection output D ₁ is taken out from this. Similarly, the stator winding L ₂ and the power generation winding G ₂ are The detection output D 2 is taken out from the power generation winding G ₂ by connecting it to the primary and secondary windings of the transformer T ₂ respectively, and the detection outputs D ₁ and _{D 2 of} each set are connected to the zero cross as shown in Fig. 10. They are added to the detectors 20 and 21, respectively, to convert them into two-phase pulses O _A and O _B , and added to the two-phase-four-phase separation circuit 22 to receive four-phase pulses _{1 and 1} as shown in FIG.
₂ , ₃ , _{and 4} are taken out, and these four-phase pulses are selected and applied to the stepping motor 25 via an excitation selection circuit 23 that specifies the excitation phase and a four-phase bipolar drive circuit 24.

Since the stepping motor of the present invention has the above-described configuration, currents I ₁ and I ₂ flow through the stator windings L ₁ and L ₂ of the stepping motor shown in FIG. 6, respectively, and the rotor rotates in the direction of the arrow. Then, a voltage equal to the sum of the induced voltage E ₁ due to the stator current I ₁ and the superpower −KsinNθ・θ due to the rotation of the rotor is induced in the generator winding G ₁ , while the voltage of the transformer T ₁ is An induced voltage _E1 is generated in the secondary winding _L2 by the current _I1 , and the secondary winding of the generator winding _G1 and the transformer _T1 is
Since l ₂ is connected in series with opposite polarity, the detection output D ₁
In this case, the induced voltage E ₁ due to the current I ₁ in the stator winding is canceled and the superpower due to the rotation of the rotor −KsinNθ・
Only θ can be output. Here, K is a constant, N is the number of pole pairs of the rotor pole teeth, and θ is the rotation angle.

Similarly, on the power generation winding G ₂ side, a stator winding current I ₂ that has an electrical phase difference of 90 degrees with respect to the current flowing in the stator winding L ₁ flows, so the detection output D ₂ is based on this. The sum of the induced voltage E ₂ and the superpower KcosNθ・θ due to the rotation of the rotor is output, and the induced voltage E ₂ due to the current ₂ due to the secondary output of the transformer T ₂ is canceled, and the detected output is only kcosNθ・θ. Become.

Figure 7 shows the voltage waveforms of detection outputs D ₁ and D ₂ in relation to the stator magnetic poles and the stable point of the rotor.
The waveforms of D ₁ and D ₂ cross the zero line at points P ₁ and P ₃ and P ₂ and P ₄ , respectively, so the outputs of detection outputs D ₁ and D ₂ are
As shown in FIG.
When converted into a pulse via
O _A and O _B are output, and the positions of P ₁ to _{P 4} can be detected.

As described above, the rotor position detection according to the present invention does not use an optical shaft encoder as in the prior art, but uses a power generation winding wound around the stator winding and a stator winding current induced in the power generation winding. There is a great advantage that can be achieved by an extremely simple configuration, in which the two-phase alternating current output obtained by the converter eliminates the induced voltage induced by the converter is converted into two-phase pulses by two zero-cross detectors.

FIG. 9 shows another embodiment of position detection according to the present invention. In this embodiment, two equal stepping motors M ₁ and M ₂ whose stator windings are bifilar wound are provided, and one stepping motor is ping motor
The stator windings L ₁ A and L ₂ of M ₁ are excitation windings,
The pair of windings _G1 and _G2 of the bifilar of each winding are used as power generation windings, the shaft of another stepping motor _M2 is fixed, and the stator windings are used as transformers _T1 and _T2, respectively. To eliminate induced voltage due to winding current.

In this embodiment, since the electric constants of the two stepping motors are well matched, there is an advantage that the induced voltage can be completely eliminated.

[Brief explanation of drawings]

Figure 1 is a sectional view of a conventional stepping motor, Figures 2a and b are sectional views taken along lines A-A and B-B in Figure 1, respectively, Figure 3a is a developed view for explaining the operation of the motor, and Figure 3a is a developed view for explaining the operation. Figure b is an explanatory diagram of the connection state of the stator windings, Figure 4 is a circuit diagram of the drive device, and Figure 5 is an explanatory diagram showing the relationship between the excitation state of the windings of each phase and the stopping point of the rotor. ,
Fig. 6 is an explanatory diagram of the stepping motor of the present invention, Fig. 7 is a diagram showing the relationship between the detected output voltage, stator magnetic poles and the stable point of the rotor, and Fig. 8 is the pulse voltage obtained from the detected output voltage. 9 is an explanatory diagram of another embodiment of the present invention, FIG. 10 is an explanatory diagram of a driving device for a stepping motor of the present invention, and FIG. 11 is an explanatory diagram of a pulse line applied to an excitation selection circuit in this driving device. It is a diagram. DESCRIPTION OF SYMBOLS 1... Pulse generation circuit, 2... 4-phase sequence circuit, 3... 4-phase drive circuit, 10... Stator yoke, 11... Stator magnetic pole, 12... Stator winding,
13...End bracket, 14...Bearing, 15
...Rotor shaft, 16, 17...Rotor yoke, 1
8... Rotor, 20, 21... Zero cross detection circuit, 22... 2-phase-4 phase separation circuit, 23... Excitation selection circuit, 24... Bipolar drive circuit, 25
...Stepping motor.

Claims (1)

[Claims] 1. A rotor equipped with a permanent magnet, a stator equipped with two sets of stator windings through which two-phase currents each having a phase difference of 90 degrees flow, and a stator with which the stator windings are energized. In a permanent magnet stepping motor consisting of a switching energization control device, a generator winding is wound over and insulated from the stator winding to generate two phase currents each having a phase difference of 90 degrees. A primary and a secondary winding having an electric constant equal to the mutual electric constant of the stator winding and the power generation winding are provided outside the stepping motor.
A transformer having a secondary winding is provided for each set, and in each set, the stator winding and the primary winding of the transformer are connected in series and connected to the drive circuit, and the generator winding and the transformer are connected in series. The secondary windings of the transformer are connected in series so as to have opposite polarities, and the detection outputs from both ends of the series circuit of each set of power generation winding and the secondary winding of the transformer are connected to a zero-cross detection circuit, respectively. A stepping motor characterized in that the energization control device is controlled by a pulse converted through the energization control device. 2. The stepping motor according to claim 1, wherein the transformer is a stepping motor having the same configuration as the stepping motor and having a fixed output shaft.